1. Field of the Invention
The present invention relates to catalysts for hydrocarbon conversion. More particularly, the invention relates to pillared clay catalysts for catalytic pyrolysis of heavy oil or residual feedstock to give the maximum yield of ethylene, propylene and butylene products and to their preparation method and application.
2. Description of Prior Art
Light olefins, including ethylene as a principal variety of the kind, are important industrial chemicals, for which the demand is increasing steadily. In the prior art, ethylene was mainly produced by means of thermal cracking process from light oil feedstock, while propylene and butylene were mainly prepared by fluid catalytic cracking (FCC) process with solid acidic catalysts.
Catalytic pyrolysis process (CPP) with heavy oil or residual feedstock is actually an art of introducing catalyst into the thermal cracking process. By the CPP process, heavy oil or residual feedstock can be converted into at relatively high yield of ethylene and propylene products at a reaction temperature lower than that of the prior thermal cracking process. The catalysts used for catalytic pyrolysis processes need to have not only the essential properties, such as good attrition resistance index and appropriate bulk density, possessed by the commercial FCC catalyst but also the distinguishing characteristics superior to the conventional FCC catalyst as follows:
(1) High Hydrothermal Stability
The reaction temperature for conventional FCC process is 460xc2x0 C.-520xc2x0 C., and reaction for thermal cracking process is 550xc2x0 C.-800xc2x0 C. Although the reaction temperature for CPP is lowered because of the use of the catalyst, it is still in the range of reaction temperatures for thermal cracking process Therefore, the catalysts used for CPP need to have high hydrothermal stability.
(2) High Converting Activity for Cracking Heavy Oil or Residual Feedstock
As the CPP technique is a process of cracking heavy oil to obtain ethylene and propylene products, the catalysts used for the process need to have high catalytic cracking activity that can convert effectively heavy oil or residual feedstock into light olefins.
(3) Good Light Olefin Selectivity
The catalysts used for CPP need to have high yields of ethylene, propylene and butylenes, low yield of dry gases and adequate coke yield to maintain thermal equilibrium of reaction and regeneration units.
The prior catalysts containing pillared clays reported in the literature are all FCC catalysts used for carbonium-ion reaction but none for the catalytic pyrolysis reaction. For example, a pillared clay catalyst reported in the Chinese patent of CN1107080A is for use in the conventional FCC process to yield more isobutene and isoamylene products (MIO catalyst). In the catalyst of the prior art, pillared rectorites prepared with a pillaring agent having a OH/Al gram mole ratio of 2.0 was used as activity component. Although the pillared clay component could improve the activity of the catalyst, it had in the meantime an adverse effect on the attrition resistance of the catalyst, hence the content of pillared clay in the catalyst of the patent is limited to less than 50 wt %. As the amount of the active component cannot be increased, consequently, the stable activities of the prior catalyst can hardly be improved. Also, in the patent the attrition resistance index data are not shown, and it implies that the attrition resistance of the prior pillared clay catalysts is inferior to commercial FCC catalysts. The prior catalysts are not catalytic pyrolysis catalysts with high stable activities and good attrition resistance index, therefore they cannot be commercialized.
The Chinese patent ZL CN 96103411.4 of the present applicant discloses a poly (vinyl alcohol) modified pillared clay catalyst for yielding more light olefin products. However, it is rather a MIO catalyst used for conventional FCC process to produce isobutene and isomyalene, than catalytic pyrolysis catalyst used for CPP to produce ethylene and propylene. In the catalyst, polyvinyl alcohol-modified pillared clay vinyl alcohol can improve the activity of catalyst, but at the same time has negative effect on the attrition resistance index of the catalyst. In the patent there is also no data about attrition resistance index and catalytic pyrolysis properties of the catalyst, this implies that the catalyst does not possess good attrition resistance index and catalytic pyrolysis properties. It is impossible to withstand the severity of CPP. Up to now the catalyst has not been commercialized.
In the Chinese patent of Z L 92109775.1 the present applicant disclosed a CCP method for petroleum hydrocarbon, wherein a pillared clay catalyst for conventional catalytic cracking process, CRP-1 (commodity trademark) catalyst and a mixture of the above two catalysts were used. Among them, the pillared clay catalyst was a pillared rectorite catalyst containing 5 wt % USY molecular sieves prepared according to the process disclosed in Z L CN 87104718, which was only a conventional FCC catalyst; and the CRP-1 catalyst was prepared by using high silicon pentasil structure zeolites containing rare earth in framework (CN 1058382A), which was also used in conventional FCC process to yield more light olefin products. Although the pillared clay catalyst of the patent had an ethylene yield of over 20 wt % and the total C2=xe2x80x94C4= yields of around 50 wt % at an average reaction temperature of 700xc2x0 C., it did not result from the catalyst after the deactivating treatment at 790xc2x0 C. or 800xc2x0 C. for 17 hours with 100% steam. Instead, only the performance of the catalyst treated at 760xc2x0 C. for 6 hours with 100% steam, indicated that the hydrothermal stability of the catalyst is impossible to meet the severity of the CPP. Up to now, no catalytic pyrolysis catalyst with good attrition resistance index, high hydrothermal stability and good selectivity to ethylene and propylene is reported in any of the prior art.
An object of the present invention is to provide a series of pillared clay catalysts that can be used in catalytic pyrolysis process for cracking heavy oil or residual feedstock to yield more ethylene, propylene and butylene products. The said catalysts comprise pillared clays with high alkalized degree, molecular sieves, matrix, bonding agents and modifying compositions. The catalysts have excellent hydrothermal stability, high catalytic activity for converting heavy oil or residual feedstock, good selectivity to light olefins, adequate coke yield and attrition resistance index and apparent bulk density in accordance with demands of FCC catalyst as well.
Another object of the present invention is to provide a method for preparation of the catalysts comprising the steps of mixing slurries of all the components of said catalysts, spray drying to form microspheric shapes, preparing pillaring agents with high alkalized degree, pillaring reaction and adding modifying components.
A further object of the present invention is to provide applications of the said catalyst products. The catalysts of the present invention are suitable for use as catalysts for hydrocarbon conversion, including CPP catalyst for producing ethylene and propylene, MIO catalyst for maximum isobutene and isoamylene yields, and FCC catalyst for cracking heavy oil or residual feedstock into gasoline and light cycle oil. Besides, the catalysts of the present invention can also be used as adsorbents and catalyst supports.
The catalysts of the present invention comprise the following compositions:
1. 30-75 wt % pillared clay compositions prepared by aluminum pillaring agents of high alkalized degree;
2. 10-40 wt % Bonding agent compositions of inorganic oxides
3. 0-30wt % High silicon zeolites with pentasil structure or y-type zeolites or mixtures thereof.
4. 0-10 wt % Modified compositions; and
5. 0-50 wt % Kaoinite matrix compositions.
Herein the pillared clay compositions with high alkalized degree are important active components of the catalysts for converting heavy feedstock. The special pillared clay compositions have excellent hydrothermal stability. They are aluminum pillared clays that take a polymerized aluminum chlorohydroxide or aluminum-sol with a mole ratio of OH/Al up to around 2.5 as precursor of propped pillars between two near 2:1 clay layers. Herein said clays are selected from a naturally occurring or chemically synthesized group consisting of swelling regular interstratified mineral clay or swelling single mineral clay series including rectorites or smecites, preferably rectorites and smectites. Their structural characteristics are described in the ZL CN 87104718.
Herein the bonding agents of inorganic oxides are formed by drying and calcining sol or gel substances containing aluminum, silicon, zirconium or mixtures thereof or the above mentioned substances modified by compounds containing phosphorus or polyethylene glycol. The said sol or gel substances are preferably aluminum-sol or pseudoboemite-sol or gel or the mixtures thereof, or that modified by polyethylene glycol.
Herein the said high silicon zeolites of pentasil structure or Y-type zeolites are auxiliary active components used for promoting the selectivities to light olefins and the catalytic activities of catalysts. The high silicon zeolites of pentasil structure are selected from ZSM-5 or ZRP series, which have similar pentasil structures and high hydrothennal stability. The pentasil zeolites are preferably ZRP series zeolites or ZSM-5 zeolites the derivatives of ZRP modified by compounds containing phosphorus (P) or magnesium (Mg) or aluminum (Al) or potassium (K) or tin (Sn) or the compounds or mixtures thereof. The Y-type zeolites are selected from a group consisting of REY, USY, REUSY zeolites or their derivatives modified by the compounds containing P, Mg, Al, K or Sn. The Y-type zeolites are able to enhance stability and activity of the catalysts.
Herein the predecessor of the said modifying components are selected from a group consisting of compounds containing P or Mg or Al or K or Sn or the mixtures or compounds thereof or polyethylene glycol. The modifying components containing P or Mg or Al or K or polyethylene glycol are used to improve the attrition resistance index and light olefin selectivity of the catalysts. The modifying components containing Sn can enhance hydrothermal stability of the catalysts.
The kaolinite matrix is preferably halloysites from the kaolin family.
The catalysts of the present invention are prepared by the steps of mixing the pillared clay, bonding agent, zeolites and kaolinite matrix from the kaolin family in the desired amounts to obtain a slurry, spray drying to form microspheric shapes, pillaring reaction and adding modifying components. The detailed preparation steps are as follows:
1. Mixing and spray drying to form microspheric semi-finished products
(1) Changing Ca-type swelling mineral clays as starting raw into Na-type or RE-type swelling mineral clays by means of conventional ion exchange method;
(2) Mixing the Na or RE-type swelling mineral clays, predecessor of bonding agents, zeolites, kaolinite matrix from kaolin family and deionized H2O in preset amounts quired quantity and spray-drying to form microspheric semi-finished products.
2. Pillaring Reaction and Aging Process
(1) Diluting commercially available aluminum-sol or polymerized aluminum chlorohydroxide prepared by prior method (according to U.S. Pat. No. 4,176,090 or U.S. Pat. No. 4,248,739) to 10-100 mmol Al/L and then aging at 65-75xc2x0 C. for 2-12 hours and holding a pH of 5-6 by dropwise addition of NH4OH or NaOH aqueous solution as needed, and then aging the resulting solution at room temperature for 2-12 hours. Thereby the high alkalized pillaring agent with OH/Al mole ratio of 2.5 is successfully obtained.
(2) Adding the RE-rectorites or Na-rectorites to the pillaring agent according to load ratio of 2.0-10.0 milligram atom aluminum per gram clay and aging the reaction mixtures at 65-75xc2x0 C. for 2-3 hours while holding the pH of 5-6 by dropwise addition of NH4OH aqueous solution. Followed by filtering, washing and drying by conventional method and calcinating at 650xc2x0 C. for 1-3 hours.
3. Adding the Modifying Components
(1) Polyethylene glycol, as a modifying component, can be added at the mixing slurry step before spray drying or at pillaring reaction or aging process after spray drying to form microspheric shapes.
(2) Compounds containing P or Mg or Al or K or Sn, as modifying components, can be added to the catalysts by impregnating zeolites before mixing and spray drying or impregnating microspheric catalysts after pillaring reaction and calcination with solutions containing the above modifying components. The impregnating solution contain the modifying components with a concentration of 0.1-5 gram per liter.
Herein said pillared clays, as starting raw, a naturally occurring or chemically synthesized group of swelling regular interstratified mineral clays, including rectorites or swelling single mineral clay sequences including smectites. The said clays are preferably rectorites or smectites whose structural characteristics are shown in the ZL CN 87104718.
The said bonding agents are inorganic oxides formed by drying and calcinating sol and get substance, which is selected from sol and gel substance containing aluminum or silicon or zirconium, or mixture thereof, or derivatives thereof modified by phosphorus-containing compounds or polyethylene glycol, preferably selected from aluminum-sol or pseudoboemite-sol or gel or mixture thereof or derivatives thereof modified by polyethylene glycol or combination thereof.
Herein the said modifying components are preferably selected from a group consisting of commercial available phosphates containing Mg, Al, K or SnCl2 aqueous solution with chlorhydric acid or compounds formed by reacting phosphoric acid (H3PO4) with Mg(OH)2, Mg(A)2, MgCl2 or KOH or aluminum-sol.
The outstanding features of the present invention as compared with the prior arts are as follows:
1. The catalyst products provided by the present invention have the best ingredients and performance of the catalytic pyrolysis catalysts. The special pillared clays with high alkalized degree (OH/Al ration of around 2.5) in the ingredients of the catalysts are adopted as the principal active component. They have excellent hydrothermal stability, high catalytic activity for cracking heavy oil or residual feedstock and low hydrogen transfer activity that are advantageous to retain the olefins. So, the catalysts provided by the present invention are much better than that of Y-zeolite catalysts used currently extensively in most refineries in respect to meeting the requirement of the catalytic pyrolysis process. The ZRP of ZSM-5 series zeolite compositions im the ingredients of catalysts impart to the said catalysts much better light olefin selectively than that of the conventional cracking catalysts. Especially, ZRP series of ZSM-5 zeolite compositions combined with modifying components can further enhance light olefin yield and hydrothermal stability as well. So, after sever hydrothermal deactivating treatment the products of the present invention retain still high olefin yield. Also, owing to the use of bonding agents modified by polyethylene glycol or compounds containing phosphous in preparation of the catalysts, the good attrition resistance index of the catalyst is easily obtained. Therefore, in the case of increasing the contents of pillared clays and zeolites in the catalysts, the catalysts can still maintain adequate attrition resistance index as good as commercial catalysts. The rational ingredients of the catalysts in the present invention result in excellent performances of the catalyst. After aging and deactivating treatment at 790xc2x0 C. for 14 hours with 100% steam, the catalysts give an ethylene yield of 21.2 wt %, a propylene yield of 22.2 wt %, and the total C2=xe2x80x94C4= yields of 54.0 wt % under the evaluation conditions of an average reaction temperature of 700xc2x0 C., catalyst to oil ratio of 10, weight hourly space velocity (WHSV) of 10 hours xe2x88x921, water injecting quantity to feedstock of 80 wt %. However, only under easing deactivation treatment conditions into steam treatment at 760xc2x0 C. for 6 hours can the prior catalyst give an ethylene yield of 21.0 wt %, a propylene yield of 18.0 wt %, and the total C2=xe2x80x94C4= yields of 50 wt %. Apparently, the catalysts of the present invention have stable activity and light olefin selectively much better than that of prior catalysts. hydrogen transfer activity that are advantageous to retain the olefins. So, the catalysts provided by the present invention are much better than Y-zeolite catalysts used currently extensively in most refineries in respect of meeting the requirement of catalytic pyrolysis process. The ZRP or ZSM-5 series zeolite impart the said catalysts much better light olefin selectivity than that of the conventional cracking catalysts. Especially, when ZRP series or ZSM-5 zeolite compositions are used in combination with modifying components light olefin yield and hydrothermal stability can be further enhanced as well. So, after severe hydrothermal deactivating treatment the products of the present invention retain still high light olefin yield. Also, owing to the use of bonding agents modified by polyethylene glycol or compounds containing phosphorus in preparation of the catalyst, the good attrition resistance index of the catalyst is easily obtained. Therefore, in the case of increasing the contents of pillared clays and zeolites in the catalysts, the catalysts can still maintain adequate attrition resistance index as good as commercial catalysts. The rational ingredients of the catalysts in the present invention result in excellent performances of the catalyst. After aging and deactivating treatment at 790xc2x0 C. for 14 hours with 100% steam, the said catalysts give an ethylene yield of 21.2 wt %, a propylene yield of 22.2 wt %, and the total C2=xe2x80x94C4= yields of 54.0 wt % under the evaluation conditions of an average reaction temperature of 700xc2x0 C., catalyst to oil ratio of 10, weight hourly space velocity (WHSV) of 10 hoursxe2x88x921, water injecting quantity to feedstock of 80 wt %. However, only under easing deactivation treatment conditions into steam treatment at 760xc2x0 C. for 6 hours can the prior catalyst give an ethylene yield of 21.0 wt %, a propylene yield of 18.0 wt %, and the total C2=xe2x80x94C4= yields of 50 wt %. Apparently, the catalysts of the present invention have stable activity and light olefin selectivity much better than that of prior catalysts.
2. The catalyst products of the present invention have extensive uses in the petroleum refining industry. They can be used as catalysts of hydrocarbon conversion, such as catalytic pyrolysis catalyst (CCP-Cataylst), maximum isomerization olefin catalyst (MIO-catalyst) and fluid cracking catalyst (FCC-catalyst). The catalysts of the present invention may be combined with various other elements by an impregnating method to meet the need for special catalysts. The catalysts can also be combined with other catalysts for use in some processes of specific objects. The products can also be used as adsorbents and carriers. However, they are especially suitable to be used in catalytic pyrolysis processes for cracking heavy oil to give the maximum yields of ethylene, propylene and butylene products.
Preparing procedures provided by the present invention are easy to be put into effect in commercial scale. In the prior preparation method of first spray drying to form microspheric shapes and then pillaring reaction (ZLCN87105686), due to the effect of reversible solubility of Al-sol bonding agent on attrition resistance index of microspheric catalysts, after pillaring reaction have attrition resistance index of the catalysts is usually lower than that of samples before pillaring reaction. In the preparation method of the present invention, new techniques of adding polyethylene glycol to a pillaring agent or impregnating zeolites or catalysts with compounds containing phosphorus are adopted. The modifying components contribute to the improvement in the properties of Al-sol or Al-gel bonding agents. As a result, the attrition resistance index of the catalysts is improved to the level of commercial catalyst. The said method disclosed by the present invention is easy to operate and to be carried out in commercial sale.
The present method for promoting attrition resistance index of catalysts by adding polyethylene glycol or phosphorous containing compounds is also suitable for preparing other microspheric catalysts containing Al-sol or Al-gel.